0.8.13.1:

	Implement MAP-REFERENCING-OBJECTS, and make the implementation
	of LIST-REFERENCING-OBJECTS use it.
	... note potential badness of cutoff point in space search.
		(could this be the problem in ROOM T?)
	Improvements to stale-symbols script.
	... if there is more than one reference, don't bother chasing
		all the others down;
	... closures can contain stuff;
	... print symbols and references a little more nicely.